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<title>Debugging with GDB: Finish Breakpoints in Python</title>

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<a name="Finish-Breakpoints-in-Python"></a>
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<a name="Finish-Breakpoints"></a>
<h4 class="subsubsection">23.2.2.30 Finish Breakpoints</h4>

<a name="index-python-finish-breakpoints"></a>
<a name="index-gdb_002eFinishBreakpoint"></a>

<p>A finish breakpoint is a temporary breakpoint set at the return address of
a frame, based on the <code>finish</code> command.  <code>gdb.FinishBreakpoint</code>
extends <code>gdb.Breakpoint</code>.  The underlying breakpoint will be disabled 
and deleted when the execution will run out of the breakpoint scope (i.e. 
<code>Breakpoint.stop</code> or <code>FinishBreakpoint.out_of_scope</code> triggered).
Finish breakpoints are thread specific and must be create with the right 
thread selected.  
</p> 
<dl>
<dt><a name="index-FinishBreakpoint_002e_005f_005finit_005f_005f"></a>Function: <strong>FinishBreakpoint.__init__</strong> <em>(<span class="roman">[</span>frame<span class="roman">]</span> <span class="roman">[</span>, internal<span class="roman">]</span>)</em></dt>
<dd><p>Create a finish breakpoint at the return address of the <code>gdb.Frame</code>
object <var>frame</var>.  If <var>frame</var> is not provided, this defaults to the
newest frame.  The optional <var>internal</var> argument allows the breakpoint to
become invisible to the user.  See <a href="Breakpoints-In-Python.html#Breakpoints-In-Python">Breakpoints In Python</a>, for further 
details about this argument.
</p></dd></dl>

<dl>
<dt><a name="index-FinishBreakpoint_002eout_005fof_005fscope"></a>Function: <strong>FinishBreakpoint.out_of_scope</strong> <em>(self)</em></dt>
<dd><p>In some circumstances (e.g. <code>longjmp</code>, C<tt>++</tt> exceptions, <small>GDB</small> 
<code>return</code> command, &hellip;), a function may not properly terminate, and
thus never hit the finish breakpoint.  When <small>GDB</small> notices such a
situation, the <code>out_of_scope</code> callback will be triggered.
</p>
<p>You may want to sub-class <code>gdb.FinishBreakpoint</code> and override this
method:
</p>
<div class="smallexample">
<pre class="smallexample">class MyFinishBreakpoint (gdb.FinishBreakpoint)
    def stop (self):
        print &quot;normal finish&quot;
        return True
    
    def out_of_scope ():
        print &quot;abnormal finish&quot;
</pre></div>
</dd></dl>

<dl>
<dt><a name="index-FinishBreakpoint_002ereturn_005fvalue"></a>Variable: <strong>FinishBreakpoint.return_value</strong></dt>
<dd><p>When <small>GDB</small> is stopped at a finish breakpoint and the frame 
used to build the <code>gdb.FinishBreakpoint</code> object had debug symbols, this
attribute will contain a <code>gdb.Value</code> object corresponding to the return
value of the function.  The value will be <code>None</code> if the function return 
type is <code>void</code> or if the return value was not computable.  This attribute
is not writable.
</p></dd></dl>

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